Do you need to wipe data when flashing kernels ? No. You shouldn't need to wipe cache/Dalvik either, though do it if the developer of the kernel says to in the flashing instructions for the kernel.
How to determine rom compatibility for a kernel ? Read the first page of the thread devoted to the kernel. Should tell you what it's compatible with, if it doesn't, ask in the kernel thread. The worst thing that can happen if you flash & it isn't compatible is you'll end up with bootloop. Unlikely to brick your phone outright unless you're one of the 0.000001% of people who end up with a bad flash full stop.
If it's important enough to cause you grief if it's lost, back it up. No excuses
Trolling for thanks is lame
Does Samsung's auto-brightness implementation crap drive you to self-harm ? A solution !
Probably the best thread ever posted on XDA
Failure to search is the leading cause of male impotence on XDA
If you don't know how to recover if things go wrong, what are you doing flashing custom roms ?